Research On Physical Layer Security Techniques To Against Active Eavesdropping

There are several characteristics of wireless channel,such that space-time uniqueness,short-time reciprocity,fast time-varying,unpredictable and so on.Based on these properties of wireless channel,a lot of physical layer schemes are proposed to improve the security of wireless communication.However,most of the research assumed that the prefect channel state information(CSI)can be acquired,which was a much difficult problem.They ignored the importance of training phase before the data transmission via downlink channel.In Time division duplex(TDD)systems,inaccurate channel estimation occurs if the illegal user sends the identical pilot sequence as legitimate user at the same time to the base station during the training phase,which will lead the information between legitimate users leakage to the illegal user.This is so called “pilot attack”.We studied and analyzed the influence of the pilot attack on the wireless communication system,and two schemes to detect the active eavesdropper which conduct pilot attack are proposed.The main job are as follows:(1)We studied and analyzed the influence of pilot attack on wireless communication of TDD systems.We found that the pilot attack can cause a serious threat to the security of wireless communication systems form the theoretical analysis and simulation result.(2)To detect whether the active eavesdropper which conduct the pilot attack present or not,we proposed a scheme which based on random orthogonal pilots,detailed analysis of the proposed scheme were given to prove the performance of the scheme.The computer simulation shows that the proposed scheme has a good detection performance.(3)A method which based on blind signal separation were proposed to detect whether the active eavesdropper present or not,detailed analysis of the proposed method were given to prove the performance of the method.The computer simulation shows that the proposed scheme has a good detection performance.